Animals And Antibiotic Resistance

Some estimates suggest that antibiotic usage amongst animals is almost double that of usage amongst humans. Because antibiotic misuse is the major cause of anti-microbial resistance, food-producing animals have become an important reservoir of bacteriasuch as E. coli and Salmonella spp that are resistant to third generation antibiotics. There is growing concern regarding the possible consequences on human health.

In 2006, the use of antibiotics as growth promoters was banned in Europe. Yet, this practice continues in many countries as much of antibiotics use on animals is for growth promotion and infection prevention rather than to treat infections. Transmission of bacteria from animals to humans can occur via direct contact, environmental contamination, or via the food chain. International trade in food products means contaminated food is a very efficient mode for the transmission of antibiotic resistance.

In the Netherlands, 44 percent of veterinarians are colonized by livestock-associated methicillin-resistant Staphylococcus aureus (also known as MRSA), a bacterium critical to human health. A recent study from the Netherlands demonstrated significant similarity in E.coli strains found in retail chicken meat and humans. This provides strong evidence of the link between antibiotic resistance in animals and human health. Approximately 90 percent of retail chicken samples were contaminated with the bacteria. A similar proportion has been found in retail meat in Spain and Switzerland.

Recent reports from several European countries have demonstrated that raw retail chicken meat is commonly contaminated with E.coli resistant to third generation cephalosporins. But there are alternatives. In Denmark, strict policies to control the use of antibiotics have resulted in a 60 percent reduction of contaminations over the period 1994 to 2001. At the same time, the number of pigs being produced increased.

Dr Andrew Stewardson, Research Fellow at the University of Geneva Hospitals, says “successful initiatives regarding the rational use of antibiotics… such as those in Denmark, have demonstrated that change is possible without a major negative impact on the food-production industry.”

The E.coli strain responsible for the outbreak of haemolytic uraemic syndrome in Europe in 2011 is thought to have been spread in contaminated sprouts, affecting 36 facilities. The same year, the European Food Safety Authority released a report about the public health risk posed by certain types of antibiotics in food and food animals. It concluded that “prioritisation is complex, but it is considered that a highly effective control option would be to stop all uses of cephalosporins, or to restrict their use to specific circumstances. As co-resistance is an important issue, it is also of high priority to decrease the total anti-microbial use in animal production in the EU.”